The invention relates to the field of polarized lightwave reflectometry methods, also known as polarization optical time domain reflectometry (POTDR). Polarized lightwave reflectometry or POTDR makes it possible to obtain at least a qualitative estimate of the polarization mode dispersion (PMD) of optical fibers having a high degree of mode coupling, with dispersion being expressed in picoseconds per root kilometer (ps/km1/2). POTDR makes it possible to verify uniformity of PMD along optical fibers. This makes it possible to identify and select good segments of an optical fiber (i.e. segments presenting a low PMD coefficient). Since PMD in an optical fiber is due to birefringence in said optical fiber, analyzing a polarized lightwave that has passed along an optical function makes it possible, qualitatively, to evaluate the birefringence of said optical fiber, and consequently to derive a qualitative estimate of its PMD. PMD can be evaluated either locally, i.e. over a portion of the optical fiber to be tested, said optical fiber portion preferably being at least 1 kilometer (km) long, or else overall, i.e. over the entire length of the optical fiber to be tested. Since POTDR involves a signal that has been back-scattered, it suffices to have access to one end only of the optical fiber to be tested or of the cable containing the optical fiber to be tested. It is advantageous for the PMD of an optical fiber to be uniform, known, and low.
In the prior art, e.g. as described in the article “Distributed PMD measurement with a polarization-OTDR in optical fibers” written by B. Huttener and published Mar. 10, 1999 in the “Journal of Lightwave Technology”, 17, pp 1843–1948, 1999, or else in the article “Single-end polarization dispersion measurement by back-reflected spectra through a linear polarizer” written by Andrea Galtarossa and published on Oct. 10, 1999 in “Journal of Lightwave Technology”, polarized lightwave reflectometry methods are known. Nevertheless, those methods are based on sending a single linearly polarized light signal from which one or more parameters are extracted, such as degree of polarization (DOP) or differential group delay (DGD) for example, from which the mode dispersion of the polarization is evaluated. The methods proposed can be described as being semi-quantitative insofar as firstly by giving a value for the polarization mode dispersion coefficient they represent a significant improvement over purely qualitative methods, and secondly their accuracy is limited and not sufficient for certain applications.